Topology first, then the gap between the VA figure and the watt figure · review

Master U-Power 650 VA rated at 360 W, with two runtimes quoted per device rather than per watt review

A six-hundred-and-fifty volt-ampere unit that prints a watt figure beside it, quotes two runtimes against named devices rather than against a load in watts, and never says which arrangement it uses or what shape its output takes on battery.

By Jean-Benoit Buisson

The bottom line Both power figures on the label and a battery described well enough to reorder, on a page that then says nothing about topology or waveform. The two runtimes read generously until it becomes clear that neither names a load in watts, which is what a runtime figure needs before it means anything.

On the listing

An uninterruptible power supply rated at 650 VA with 360 W of constant output and two Schuko sockets; maximum protection claimed against cuts, surges and electromagnetic disturbance, with a runtime given as 10 minutes for a computer or 40 minutes for a modem and router, and protection named for Windows machines, video recorders and surveillance systems, modems on ADSL and on fibre, and tills; a claim that the two Schuko outputs let anyone install the unit quickly and safely; the same claim again, word for word; a design said to make changing the battery easy and to keep the unit working over a long period, with RJ-45 protection for networked equipment; and a 12 V 7 Ah battery supplied, replaceable by packs of 12 V 7 Ah, 12 V 7.2 Ah or 12 V 9 Ah for a longer runtime.

650 volt-amperes and 360 watts

Two ratings, two lines, and no arithmetic between them. Volt-amperes are apparent power and watts are real power, and the ratio a maker assumes between them is its own choice rather than a fixed number. Here the pair is 650 and 360. The second figure is the one a load is added up against, because everything plugged in has a consumption in watts and the total has to fit inside 360. The first is the figure printed largest. Six of the eight pages in this batch print both; this site prints them apart and turns neither into the other.

Ten minutes for a computer, forty for a modem and router

The first bullet quotes two runtimes and names a device for each. That is more than a bare number and less than a measurement. A computer is not a consumption: a small machine sitting idle and a desktop with a large graphics card differ by a factor of several, and that difference lands directly on the minutes. The second figure being four times the first says the maker assumes a much lighter load for network equipment, and it never says how much lighter. A runtime that can be checked reads as minutes at a stated number of watts.

The battery, and the three sizes that replace it

12 V and 7 Ah supplied, with 7 Ah, 7.2 Ah and 9 Ah listed as fitting. This is the most practical sentence on the page. A battery is a consumable, it is the part that ends the working life of one of these units, and a listing that gives the size and the alternatives lets the second purchase be planned before the first is made. The chemistry is not named. Fitting a replacement, and anything else to do with the mains side of the unit, belongs to the instructions in the box.

The two bullets that say the same thing

The second and third bullets are identical, word for word: the two Schuko outputs, and a claim that installation is quick and safe. One of the five slots on the page is therefore spent twice, and it is spent on the claim that needed it least. Counted honestly, this listing has four bullets, and the missing fifth is where a runtime with a load in watts, or a waveform, could have gone.

Before ordering

Ask for a runtime in minutes at a stated number of watts, and ask which of the three arrangements this is. The power ratings and the battery are settled by the page; the two lines that decide whether it suits a particular machine are not, and on the waveform it is the manufacturer of that machine who answers.

Availability

Priced from 42 € to 50 € across the German, French and Spanish Amazon stores the day this page was checked.

The Italian Amazon price runs past 1.6× the cheapest store. A gap that size normally marks a reshipper and not a seller in the country, so that listing stays out of the range above.

In the British Amazon catalogue with no live offer against it: the reference exists, nobody is filling it.

The American Amazon store returned nothing at all, so the buy button there opens a search in that country rather than a page that would not load.

Every figure in this section is what Keepa held on the day this page was last updated. Stock and prices move without warning.

Prices quoted in this text were read on 10 September 2026. The live price is at the top of the page.

Where it holds up, and where it stops

Strengths

Both power figures are printed, so the watt rating does not have to be sought from the maker before a load can be added up
The battery is described by voltage and by amp-hours, and three sizes that fit are listed by size rather than by part number
The fourth bullet treats the battery as a consumable and says the case is built around changing it

Compromises

The two runtimes are quoted against a computer and against a modem-router, and neither device is given a consumption
Topology is never named, and it is the line that separates the three arrangements on this shelf
No waveform is stated, which is the property a power supply with active correction is most particular about

Specifications

Topology	Not published on the listing — the title and the five bullets name the unit as an uninterruptible power supply and never say whether the load runs from the mains until a relay hands it over, from a transformer-corrected supply, or from the inverter at all times
Stated classification	Not published on the listing — no classification code from the standard that covers these units appears, on a page that also leaves out the topology such a code would describe
VA rating	650 VA — printed in the title. It is apparent power, the figure this shelf is normally sold on, and it is reported on its own line because it is not the watt figure below it
Watt rating	360 W — printed in the title, inside a phrase about constant output that names a voltage rather than a power. The figure carries the watt unit and is reported as published; the wording around it is the maker’s own
Stated runtime at a named load	10 minutes for a computer, or 40 minutes for a modem-router — stated in the first bullet. The load is named as a class of device and never as a figure in watts, so neither time can be checked against what a particular machine draws
Output waveform	Not published on the listing — nothing on the page says whether the output on battery is a sine wave or a stepped approximation of one
Socket count	Two — printed in the title and counted again in the second bullet
Socket type	Schuko — printed in the title and named again in the second bullet. Whether both carry the battery, or one is filtered only, is not stated
Battery type	12 V, 7 Ah — stated in the fifth bullet as the pack supplied. No chemistry is named, so nothing says which of the sealed types is inside
Battery replaceability	Changeable — the fourth bullet describes a design built around an easy battery change, and the fifth names three sizes that fit as replacements: 12 V 7 Ah, 12 V 7.2 Ah and 12 V 9 Ah
Communication port	Not published on the listing — the fourth bullet names an RJ-45 protection path for networked equipment, which is a protected line rather than a socket that reports the state of the unit to a computer
Amazon reference	B0D45F9WD1 (same reference on 5 Amazon marketplaces)
EAN	8435543314239

The questions that come up before an order

Why is 650 VA not 650 W?

Because the two measure different things. Volt-amperes are apparent power, the product of voltage and current; watts are real power, what the load actually consumes. The relation between them is the power factor the maker assumes when it rates the unit, and it is a choice rather than a constant. That is why the watt figure is always the smaller of the two and why turning one into the other from outside produces a number nobody published. This page prints both, 650 and 360, and this site reports each as published on its own line.

What does a runtime quoted per device leave out?

The consumption. Ten minutes for a computer assumes a computer of some particular draw, and two machines on the same desk can differ several times over. Forty minutes for a modem and a router assumes a much lighter load, which is why the second figure is four times the first, and the page never says how much lighter. A runtime that can be checked is quoted as minutes at a stated number of watts. Neither of these two is.